The effect of the activator materials on the structure and mechanical properties of SiC coatings

Purpose This study aims to develop and assess a silicon carbide (SiC) coating on graphite to improve its mechanical properties and thereby increase its resistance to erosion. Design/methodology/approach The synthesis of SiC coating was achieved through the pack cementation process, using two various activators, which were NH4Cl and CrCl3.6H2O at a temperature of 1,500°C for 2 h under argon flow. This study examined the effect of activator type through the analysis of microstructures, phase identification and hardness of SiC coatings. Findings The as-coated specimens showed the formation of the β-SiC phase with more than 150 µm thickness on the graphite surface. Moreover, the hardness value of the coated specimen was greater than that of the uncoated graphite specimen, especially the SiC coating synthesized with CrCl3.6H2O activator, resulting in a surface hardness value of approximately 1,655 ± 75 HV0.3. CrCl3.6H2O as an activator showed a better performance of depositing Si on graphite substrate because of the higher partial pressure of halide species. Originality/value The improvement of the structure and mechanical properties of SiC coating could lead to the high oxidation and erosion resistance of graphite. To understand the erosion process, the mechanisms of the erosion process have also been studied.